SHGetInstanceExplorer function (shlobj_core.h)

Retrieves an interface that allows hosted Shell extensions and other components to prevent their host process from closing prematurely. The host process is typically Windows Explorer or Windows Internet Explorer, but this function can also be used by other applications.


SHSTDAPI SHGetInstanceExplorer(
  [out] IUnknown **ppunk


[out] ppunk

Type: IUnknown**

When this function returns successfully, contains the address of the host process' IUnknown interface pointer. This is a free-threaded interface used to prevent the host process from terminating. If the function call fails, this value is set to NULL.

Return value


If this function succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.


There are a number of components, such as Shell extension handlers, that are implemented as DLLs and run in a host process such as Windows Explorer (Explorer.exe) or Internet Explorer (Iexplore.exe). Typically, when the user closes the host process, the component is shut down immediately as well. Such an abrupt termination can create problems for some components. For example, if a component is using a background thread to download data or run user-interface functions, it might need additional time to safely shut itself down.

SHGetInstanceExplorer allows components that run in a host process to hold a reference on the host process. SHGetInstanceExplorer increments the host's reference count and returns a pointer to the host's IUnknown interface. By holding that reference, a component can prevent the host process from closing prematurely. After the component has completed its necessary processing, it should call (*ppunk)->Release to release the host's reference and allow the process to terminate.

Note  If SHGetInstanceExplorer is successful, the component must release the host's reference when it is no longer needed. Otherwise, all resources associated with the process will remain in memory. The IUnknown interface pointed to by *ppunk can only be used to release this reference. Components cannot use (*ppunk)->QueryInterface to request other interface pointers.
SHGetInstanceExplorer succeeds only if it is called from from an application which had previously called SHSetInstanceExplorer to set a process reference.


Minimum supported client Windows XP [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header shlobj_core.h (include Shlobj.h)
Library Shell32.lib
DLL Shell32.dll (version 4.0 or later)